High pressure die casting apparatus

ABSTRACT

In a pressure die casting apparatus, a die locking device in which a locking member is pivotably mounted on a frame and is movable into a position opposing a die part mount to have the force on the die part in the casting operation act through the locking member onto the frame substantially in the direction of that force. Another die locking device employs a main cylinder and piston assembly and an auxiliary cylinder and piston assembly with the chambers of the two cylinders interconnected whereby actuation of the auxiliary piston locks pressurized fluid in the main chamber. A sprue ejector mechanism has a plunger movable in a tubular piston rod, the end of the plunger being threaded to a collar and held to the piston rod and a cap threaded to the end of the piston rod, all for precise adjustment of the plunger in the die cavity. In the sprue ejector mechanism a fixed piston and a forwardly located free piston are mounted on the piston rod to advance the plunger suddenly into the gate of the die and then to retract the plunger from the die cavity. A mount for holding a die part comprises a pair of side channels cooperating with a central block to form a C-shaped bracket, at least one of the brackets being slidable by a rack and piston assembly to give lateral access of the die part to the mount.

United States Patent Fisher et al.

[ Dec. 23, 1975 Primary ExaminerFrancis S. l-lusar AssistantExaminer-John S. Brown [57] ABSTRACT In a pressure die castingapparatus, a die locking device in which a locking member is pivotablymounted on a frame and is movable into a position opposing a die partmount to have the force on the die part in the casting operation actthrough the locking member onto the frame substantially in the directionof that force. Another die locking device employs a main cylinder andpiston assembly and an auxiliary cylinder and piston assembly with thechambers of the two cylinders interconnected whereby actuation of theauxiliary piston locks pressurized fluid in the main chamber. A sprueejector mechanism has a plunger movable in a tubular piston rod, the endof the plunger being threaded to a collar and held to the piston rod anda cap threaded to the end of the piston rod, all for precise adjustmentof the plunger in the die cavity. In the sprue ejector mechanism a fixedpiston and a forwardly located free piston are mounted on the piston rodto advance the plunger suddenly into the gate of the die and then toretract the plunger from the die cavity. A mount for holding a die partcomprises a pair of side channels cooperating with a central block toform a C-shaped bracket, at least one of the brackets being slidable bya rack and piston assembly to give lateral access of the die part to themount.

10 Claims, 11 Drawing Figures US. Patent Dec.23, 1975 Sheet 1 of83,927,711

3 AM 000 o 7 m 2 e 1 B 2 O 9 Wm Z m m H 1 A 1 0 7 2% a $0 a U.S. PatentDec. 23, 1975 Sheet 2 of s US. Patent Dec. 23, 1975 Sheet 3 of 83,927,711

US. Patent Dec. 23, 1975 Sheet 4 0f 8 3,927,711

US. Patent Dec. 23, 1975 Sheet 5 of 8 3,927,711

OWN

wmm

v U.S Patent Dec. 23, 1975 Sheet60f8 3,927,711

US. Patent Dec. 23, 1975 Sheet70f8 3,927,711

US. Patent Dec. 23, 1975 Sheet 8 of 8 3,927,711

HIGH PRESSURE DIE CASTING APPARATUS This invention relates to pressuredie casting.

A problem in pressure die casting is the force required to ensure thatthe die is properly closed against the high internal pressure of theinjected metal. Devices presently in use employ a heavy hydrauliccylinder or a toggle mechanism assembly to close and to lock the movabledie parts. An improved device using pivotal leverage, and employing aforce acting" in the direction of closing movement of the die, isdisclosed in US. Pat. No. 3,701,377 issued Oct. 31, 1972 to Fisher GaugeLimited assignee of William F. Fisher. Such devices are not practical toovercome flashing at very high pressures, in the order of 4000 to 5000pounds per square inch, and flashing on each casting must be trimmed byan additional trim press before it is tumbled and tapped.

It is an object of the present invention to provide an improvedapparatus for releasably locking a die part in a high pressure diecasting operation, using pivotably mounted means acting substantially inthe direction of closing movement of the die part.

It is another object of the invention to provide an improved apparatus,for closing and releasably locking a die part in a high pressure diecasting operation, in which a piston in main cylinder and pistonassembly is locked by an auxiliary cylinder and piston assembly.

Another object of the invention is to provide a sprue ejector mechanismwhich is finely adjustable and has a plunger rod which is easilyremovable, and to provide an efficient cylinder and piston assembly foradvancing and retracting the sprue ejector.

A further object of the invention is to provide an improved mount forholding a die part, in which the die part may be inserted laterally intothe mount, preferably from either of two opposed directions.

An example embodiment of the invention is shown in the accompanyingdrawings in which:

FIG. I is an exploded perspective view of an injection die moldingapparatus according to the invention;

FIG. 2 is an exploded perspective view of a die for use with theapparatus of FIG. 1;

FIG. 3 is a view of a vertical die closing unit taken along line 33 ofFIG. 1, partly in cross-section;

FIG. 4 is a view taken along line 4-4 of FIG. 3;

FIG. 5 is a view of a core ejection mechanism taken along line 55 ofFIG. 1, partly in cross-section;

FIG. 5a is a view taken along line 5a5a of FIG. 5;

FIG. 6 is a view of a horizontal die closing unit in cross-section takenalong line 66 of FIG. 1;

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 6;

FIG. 8 is a view of a locking device taken along line 88 of FIG. 1;

FIG. 9 is a view similar to FIG. 8 showing the locking device inoperation;

FIG. 10 is a cross-sectional view taken along line l0l0 of FIG. 9;

The embodiment shown in the drawings comprises a frame 10 which issectioned for convenience of construction into a platform 12 carrying ahorizontal die closing unit 13, a pair of vertical columns 14, a firstcrosshead 16 carrying a vertical die closing unit 17, and a secondcrosshead 18 carrying a locking unit 20, all held together by aplurality of bolts 21 passing through aligned vertical passages 22 ineach of these vertically stacked members. Frame 10 rides on a yoke 24which is movable to seat and unseat a gate 25 of a die 26 (see FIG. 2).Die 26 is held by frame 10 on an injection nozzle (not shown) whichprojects through an aperture 27 in platform 12 (see FIG. 1), asdescribed in abovementioned US. Pat. No. 3,701,377.

A simplified example die 26, for use with the apparatus of theinvention, is shown in FIG. 2 of the drawings and comprises a lower diepart 30 having a well 34, and an upper die part 36 which closes well 34and carries a C-shaped die mount channel 37 and has a centrally locatedaperture 41. Upper die part 36 also carries an ejector plate 38 withwings 39, the ejector plate being biased upwardly by compression springs40 and having a plurality of ejection pins 42 which lie in upper diepart 36. Lower die part 30 has a lateral block 43 which carries aT-shaped die mount flange 44 and fits into an aperture 46 in the side ofthe die part. A sample die product 48 is also shown in the explodeddiagram of FIG. 2.

Vertical die closing unit 17, carried by first crosshead l6 and shown inFIGS. 3 and 4 of the drawings, comprises an hydraulic cylinder andpiston assembly 50 with a cylinder 52 fixed by an end plate 53 to abridge plate 54 of the crosshead and a piston rod 56 extending in bothdirections from the cylinder, as seen more particularly in FIG. 3 of thedrawings. Lower end 58 of piston rod 56 carries a flange 60 which isfixed to the piston rod by a bolt 62 and is receivable in die mount 37of upper die part 36 (see FIG. 2). As seen in FIG. 4, a central aperture64 in flange 60 is held closed by a compression spring 66 acting on aslide 68 which has an offset aperture 70.

An annular piston 72 fixed on piston rod 56 moves vertically in a closedchamber 74 of cylinder 52 and the piston is stepped to provide ashoulder 78 of reduced diameter which is receivable in a cylinder recess79 in the lower end of the chamber. A first port 80 opens into the upperend of chamber 74, a second port 82 opens into the lower end of thechamber, and a third port 84, larger than port 82, opens into recess 79.Ports 82 and 84 connect with passages 86 and 88 respectively in cylinder52 which lead in parallel to a common outlet 90. A check valve 92,located in passage 86, controls the outflow of fluid from port 82.

A locking plate 94 is fixed on the upper end of piston rod 56 carries apair of parallel bearing pads 96 having upwardly directed and outwardlydiverging flat faces 98. Locking plate 94 has a central aperture 100which is aligned with an axial bore 102 in piston rod 56 which is inturn aligned with aperture 64 in flange 60. Locking plate 94 alsocarries an upwardly projecting limit switch actuator 104.

A sprue ejection mechanism carried by locking plate 94, is shown indetail in FIGS. 5 and 5a of the drawings. Mechanism 110 has a verticalhydraulic cylinder and piston assembly 1 12 which is fixed in a mount114 attached to locking plate 94 by bolts 115. In assembly 112 acylinder 113 has a closed chamber 116 in which a first piston 118reciprocates. Piston 118 is annular and is integral with a piston rod119. A second, annular free piston 120, larger than first piston 118,also reciprocates in chamber 116 on piston rod 119 between piston 118and the bottom of the chamber. Chamber 116 comprises an upper bore 116aaccommodating first piston 118 and a lower, larger, bore 1 16baccommodating free piston 120 which is limited in its upper travel by ashoulder 121 formed between bores 3 116a and 116b. A first port 122opens into the upper end of upper bore 116a of chamber 116, a second,annular port 124 opens into the upper end of lower bore 116b of chamber116, and a third, annular port 126 opens into the lower end of the lowerbore l16b of chamber 116.

A plunger rod 128 passes through an axial bore 130 in piston rod 119 andthe rod carries at its lower end a plunder 132 which is threaded into asocket 134 in the rod. Plunger 132 is held against rotation by a springloaded key 136 movable by a bar 138 projecting through an aperture 140in plunger rod 128. The upper end of piston 119 projects from cylinder113 and the rod is externally threaded to receive both a laterallyprojecting bar 142 and crenellated cap 144 which is internally threaded.A spring loaded locking pin 146, mounted on bar 142, is urged intoengagement with crenellations 148 circumferentially located on cap 144.Plunger rod 128 projects upwardly through cap 144 and is threaded at itsupper end 149 to carry a locking nut 150 and a collar 151 which isthreaded internally to engagethe upper end of the plunger rod andcarries externally an annular shoulder 152 resting on the end of pistonrod 119 and a key (not shown) which is received in a transverse slot inthe end of rod 119. Cap 144 has a central aperture 153 enabling the capto pass nut 150. Bar 142 projects laterally from piston 119 below avertical damping plunger 154 which projects downwardly from an hydrauliccylinder 156 having a threaded upper post 158. An internally andexternally threaded tube 160 engages post 158 and is engaged by anextension 162 of mount 114.

Horizontal die closing unit 13, shown in FIGS. 6 and 7, is mounted onplatform 12 and projects laterally through an archway 202 in column 14.Unit 13 includes a main hydraulic cylinder and piston assembly 203having an annular piston 204 reciprocable in a closed chamber 206 of acylinder 208 which is fixed on a mounting plate 209 attached by bolts209a to platform 12 and column 14. A piston rod 210, on which piston 203is fixed, extends from each end of cylinder 208 and carries at itsforward end a C-shaped mounting bracket 212 which is engagable withT-shaped flange 44 on die part 30 of die 26 (see FIG. 2). A cylinder andpiston assembly 213 has a piston 214 which reciprocates in a closedchamber 216 of a cylinder 217 having a first port 218 in the forward endof chamber 216 and a second port 220 in the rearward end of chamber 216.A piston, rod 222 extends rearwardly from piston 214 through a bore 224in cylinder 217 and projects into a surge chamber 226 in a housing 228,to actt as a further piston. A third port 230 leads into bore 224 and anaxial passage 232 with radial passages 234 connects port 230 with surgechamber 226 when auxiliary piston 214 is at the forward end of chamber216. A passage 236 connects auxiliary chamber 216 of cylinder 217 with aport 237 opening into main chamber 206 forwardly of piston 204 whileanother passage 238 connects further chamber 226 with a port 239 openinginto main chamber 206 rearwardly of piston 204.

A second horizontal locking unit 13 may be mounted to project through anarchway 239 in the vertical column l4 opposite archway 202.

As seen in FIGS. 6 and 7, bracket 212 on piston rod 210 comprises aT-shaped central block 240 (see FIG. 1) and a pair of sliding sidechannels 242 each having a rack 244 along one side edge engagable withan idler gear 246 which is removably mounted on either of a pair of pins247 on block 240. Gear 246 meshes with a drive gear 248. Idler gear 246is shown in FIG. 7 engaging one of channels 242, the other channel beingsuitably locked to block 240 as by a pin. Drive gear 248 is keyed on ashaft 250 which is coaxially mounted in piston rod 208 for free axialrotation. The end of shaft 250 remote from drive gear 248 is supportedon a frame 252 and carries a knurled knob 254. Each channel 242 is keptfrom dropping out of bracket 212 by a pin 256 fixed in central block 240and projecting into a slot 258 in the side of channel facing the block.

Locking unit 20 is carried by second crosshead 18 as shown in FIGS. 8, 9and 10 of the drawings. A pair of parallel, horizontal bearing shafts300 having axes 301 are journally mounted on needle bearings 302 in thesecond crosshead and the bearings are protected by end caps 304, as seenin FIG. 10. Each shaft 300 has a central eccentric portion 310 with anaxis 311 offset from axis 301 of the shaft and parallel to that axis, asseen in FIG. 8. A locking arm 306 depends from each shaft 300 and isjournally mounted on eccentric portion 310 by a collar 307 and needlebearings 308, the locking arm being radial to the collar. One end of thecrank arm 312 is fixed to eccentric portion 310 by a key 314 and furthersecured to the eccentric portion by bolts 316. The other end of crankarm 312 is pivotally connected by a pin 318 to the forked free end 320of a piston rod 322 of a hydraulic jack 324 which is pivotably mountedon a block 326 fixed on first crosshead 16. Each locking arm 306 has aninternal bore 328 which houses a plunger 330 carrying a freely rotatingfollower 332 at one end. A compression spring 334 urges follower 332against eccentric 310 and maintains the lower end of plunger 330 insidebore 328. Each locking arm 306 terminates in a flat bearing face 336 andcarries stop means in the form of a lateral flange or plate 338 movablelaterally towards a cross bar 340 of second crosshead 18. Plate 338 inturn carries a stop bar 339, preferably of TEFLON (a trade mark) whichis engagable with the side of locking plate 94 on lateral movement ofplate 338 in the other direction. Eccentric 310 has a circumferentiallyoriented cam recess 342 which receives follower 332 when piston rod 322of jack 324 is extended as seen in FIG. 8. Thus follower 332 yieldablycouples collar 307 to shaft 300 for common rotation with that shaft aslong as locking arm 306 is movable laterally.

As seen in FIGS. 1 and 2, ejector plate 38 of die 26 is actuated by apair of legs 400 pivotally suspended from a pair of radial arms 402fixed on a shaft 404 which is journally mounted in bearing blocks 406fixed laterally to crosshead 16 by bolts 408. One end of shaft 404carries a crank arm 410 which is pivotably connected to an hydraulicjack 412 by a yoke 414 on the free end of a piston rod 416 of thehydraulic jack. Jack 412 is pivotably suspended from a bracket 418mounted on crosshead 18.

In the operation of the example embodiment, upper die part 36 isattached by die mount 37 to flange 60 on piston rod 56 of vertical dieclosing unit 17. As seen in FIG. 3, to close die 26, piston 72 is moveddownwardly in chamber 74 of cylinder 50 by introducing hydraulic fluidunder pressure into first port and allowing hydraulic fluid to escapefrom second and third ports 82 and 84. Because port 84 is large, morefluid will escape through that port until shoulder 78 enters recess 79as piston 72 approaches the lower end of chamber 74. This cuts offlarger port 84 from the remainder of the fluid above the shoulder-whichmust then pass out through smaller port 82, providing a cushioningeffect which. maybe regulated bycheck valve 92. This cushioning protectsthe die. a

When upper die part 36 has been closed on lower die part 30asdescribedabove, vertical die closing unit 17 is locked in position bylocking unit 20 which is shown more particularly in FIGS. 8, 9 and 10.As seen in FIG. 8, cylinder and piston assembly 50 rests on bridge plate54 with locking plate 94 fixedon piston rod 56. Locking-arms 306, whenat rest, are each displaced laterally from locking plate 94 by extendingpiston rod 322 of jack 324 ,until plate 338 is moved to a positionadjacent crossbar 340, thus giving clearance for locking plate 94 to beraised by piston rod 56 as shown in broken lines in FIG. 8. To lockpiston rod 56 in its lowered position, jacks 324 are actuated to retractpiston rods 322, which causes shaft 300 and collar 307, interlocked byfollower 332, to rotate together and thereby to swing laterally overlocking plate 94, locating bearing faces 336 above faces 98 of bearingpads 96. The lateral inward swing of each locking arm 306 is arrested bystop bar 339 coming into contact with locking plate 94, therebyarresting the rotation of collar 307 in conjunction with shaft300.However, shaft 300 continues to rotate-whereupon follower 332 moves outof recess 342 against the action of spring 334. This continued rotationof shaft 300 causes axis 311 of eccentric 310 to swing about axis 301 inthe direction of pad 98, as seen in FIG. 9, which moves collar 307 andlocking arm 306 towards bearing pad 98. This is essentially a lever ofthe third order where the load is between the fulcrum and the appliedforce. Preferablylever arm 312 swings in an arc of about 45; in thefirst 15 locking arm 306 is swung laterally to face bearing pad 98, inthe second 15 locking arm 306 is moved longitudinally to take up theclearance between bearing face 336 and bearing pad 98, and in the third15 other variables such as die thickness are taken up. The release oflocking plate 94 is effected by extending piston rods 322' from jacks324 to rotate shaft 300, causing follower 332 to seat again in recess342 of eccentric 310 by the pressure of spring 334. This releases thelocking force on bearing pad 96 and locking arm 306 thereupon swingslaterally away from locking plate 94 by the continued rotation of shaft300. It will be appreciated that the lever action of axis 311 swingingabout axis 301 and the use of anti-friction bearings 308 prevents themechanism from seizing as it woulddo if only the eccentric itself wereto be used.

To close aperture 46 in lower die part 30, block 43 is attached byflange 44 to bracket 212 on horizontal die closing unit13. As seen inFIG. 7, the manual operation of knob 254 rotates gears 246 and 248 whichraises one channel. 242,.allowing bottom .die part of die 26 to slidelaterally onto platform 12 for engagement of flange 44 by bracket 212.When flange 44 is in place, channel 242 is lowered again. Block 43 isthen ready to be moved by piston 204 into aperture 46 of lower die part30. To actuate piston 204, hydraulic fluid under pressure is introducedinto third 'port 230 and, with auxiliary piston 214 advanced againstfirst port 218 as seen in FIG. 6, the fluid passes through radialpassages 234, passage 232, chamber 226, passage 238 and port 239 intochamber 206. As piston. rod 210 is extended forwardly (to the left inthe drawing), hydraulic fluid on the other side of piston 204 escapesfrom chamber 206 through port 237 and passage 236 into auxiliary chamber216 and out through second port 220. When 6 piston rod 210 has beenfully extended forwardly (as seen in FIG. 6), hydraulic fluid underpressure is introduced into auxiliary chamber 216 through first port 218to move auxiliary-piston-214 rearwardly to move radial passages 234 outof registration with third port 230, locking piston rod 210 in its fullyextended position. Thus assembly 213 acts as an intensifier of lockingpressure, the fluid pressure in surge chamber 226 and chamber 206 ofcylinder 208 being increased by the ratio between the diameters ofpiston 214 and piston rod 222. To retract piston rod 210 rearwardly (tothe right in the drawing), hydraulic fluid under pressure is introducedthrough second port 220 into auxiliary chamber 216 which moves auxiliarypiston 214 towards first port 218 and opens chamber 226 to third port230 through radial passages 234, allowing the pressurized hydraulicfluid in chamber 206 of cylinder 208 to escape. The hydraulic fluidunder pressure introduced through second port 220 also passes throughpassage 236-into chamber 206 to move piston 204 and retract piston rod210. It will be appreciated that the operation of horizontal die closingunit 13 is controlled by suitable micro-switches not shown, as in theother operable units of the example embodiment.

When die 26 has been closed, plunger 132 is advanced into the die cavitythrough aperture 41 in upper die part 37. Referring to FIG. 5, this isachieved by introducing hydraulic fluid under pressure through port 122into chamber 116 of cylinder 113 and releasing the fluid pressure atports 124 and 126, thus moving piston 118 downwardly to meet free piston120 which rests against the lower end of chamber 116.

In this position of piston 118, plunger 132 projects into gate 25 of die26 to clear the gate of any sprue remaining from a previous casting.Plunger 132 is then withdrawn from gate 25 by introducing fluid underpressure through port 126 into chamber 116. Because the area of freepiston 120 is greater than the area of piston 118, the fluid pressureintroduced through port 126 will cause piston 120 to rise until it bearsagainst shoulder 121 betweenbores 116a and 116b of chamber 116. Avertical adjustment of plunger 132 may then be made to provide a correctgap for inflow of metal through gate 25 of die 26 and this verticaladjustment is effected by rotating rod 128. Threaded upper end portion149 of rod 128 engages collar 151 which cannot rotate because it iskeyed to the end of piston rod 119.

Plunger 132 is now in position for the casting operation to begin byadvancing die 26 onto the injection nozzle. After injection andsolidification, die 26 is withdrawn from the casting nozzle as describedin aforementioned U.S. Pat. No. 3,701,377. When die 26 is clear of theinjection nozzle, fluid pressure is released from port 126 and plunger132 is moved down once again to clear gate 25 of any sprue material.Next fluid pressure is applied to port 124 and released from port 122 toretract the punch from the casting in die 26. When bar 142 strikesdamping plunger 154 the abrupt upward movement of plunger 132 isarrested. All the above functions are precisely timed by a suitableelectronic sequence circuit, in fractions of seconds. It will be notedthat plunger 132 does not advance initially until die 26 is closed, toprevent damage to the plunger in the event that a casting has fallenonto lower die part 30.

Plunger 132, when inserted through aperture 64 of flange 60 andQthroughaperture of slide 68, acts against compression spring66. If plunger .132does not project into die aperture 49 the aperture is sealed by slide 68to prevent molten metal from being released under pressure through theaperture. The structure of sprue ejection mechanism 110 makes plunger-132 readily replacable. t

To open die 26, locking arms 306 of vertical die closing unit 17 arereleased from bearing pads 96 and swung laterally as described above,whereupon piston 56 in cylinder 22 is raised. If the cast product iscarried upwardly by upper die part 36 as piston 56 is raised, theproduct is released by actuating jack 412 (see FIG. 1) to extend pistonrod 416 downwardly, causing legs 400 to bear against wings 39 of ejectorplate 38 and forcing the ejector plate downwardly against the action ofsprings 40 (see FIG. 2).

Actuation of units 13 and 17 cause die 26 to be closed.

Plunger '132 is adjusted; to have its lower endterniinate in gate 25'ofdie 26 when pistons 118 and 120 are in their lowermost positions inchamber 116 of cylinder 114; this is done by rotating plunger'rod 128 incollar 1'51 and then turning locking nut 150 against the collar. Theplunger is then retracted out of the gate by introducing fluid underpressure through ports 122 and 126 v 8 'metal in die 26 acting throughpiston 56 and bearing plate 94, transfers that force to bolts 21 inframe 10. This construction-enables the main parts of die 26 to belocked under high pressure.

I claim:

1. In pressure die casting apparatus, a device for moving and locking adie part to close a die mounted on a die frame, comprising:

means mounting the die part on the die frame;

means to move the die part mount in a direction opposite to the forceacting on the die part when closed and charged, to close the die;

at least one locking member engagable with the die part mount when thedie is closed, said locking member being pivotably mounted on the dieframe, and

means for moving the locking member into a position between the mountand the frame whereby said force acts through the member onto the framesubstantially in the direction of said force.

2. Apparatus as claimed inclaim l in which the die part mount carries atleast one bearing means and the into chamber 116 of cylinder 114. Beingof larger diameter, free piston 120 forces piston 118 upwardly untilpiston 120 meets shoulder 121. Horizontal unit 13 islocked by theactuation of auxiliary piston 214 and vertical unit 17 is locked by theactuation of jacks 324. Die 26 is now ready for the casting operationand the die is registered over the die nozzle of the device by adjustingplatform 12 on yoke 24. The step'ofadjusting platform 12 does not haveto be repeated for each subsequent casting cycle, as explained in abovementioned U.S. Pat. No. 3,701,377. In the first step of the castingoperation plunger 132 is moved into gate 25, by releasing pressure inport 126, to remove any sprue remaining from a previous casting cycleand the plunger is then withdrawn immediately to its previous positionby re-applying pressure in port 126. In the next step die 26 is injectedwith pressurized molten metal and when the injection has been completedand the casting has solidified, ejection mechanism 18 is actuated tomove punger 132 downwardly again into gate 25 of die 26 by releasing thepressure in port 126. T 'his ejects the sprue from die gate 25 and theplunger is then immediately withdrawn upwardly out of die cavity 34releasing the pressure in port 122 and applying pressure in port 124 toraise piston l lS in chamber 116. To open die 26, (1) horizontal dieclosing unit 13 is unlocked by actuating auxiliary piston 114 andretracting piston 210, and (2).vertical die closing unit 17 is unlockedby actuating jacks 324 and raising piston 56. Upper die part 36 israised with piston 56 to plate 38 adjacent legs 400. Jack 16 is thenactuated to press ejector plate 38 against springs 40 which movesejector pins 42 against the top of the casting and forces the castingout of. upper die part 36.

It will be appreciated that the orientation of locking arms 306 ofvertical die closing unit 17, being substantially in line with the forceof the pressurized molten locking member carries a locking arm movableto have one end thereof oppose the bearing means, the locking arm beingmounted eccentrically and substantially on a shaft and the shaft beingrotatably mounted on the die frame.

3. Apparatus as claimed in claim 2 in which the shaft carries atransverse crank arm, a jack being pivotably mounted on the frame and onthe crank arm for rotation of the shaft.

4. Apparatus as claimed in clai m 1 in which the die part mount carriesa bearing pad and the frame carries a locking member comprising a shaftrotatably mounted on the die frame and having an eccentric portion, acollar rotatably mounted 'coaxially on the eccentric portion of theshaft, means yieldably coupling the collar with the shaft, a locking armradially fixed on the dollar and movable on rotation of the shaft tohave the free end of the locking arm oppose the bearing pad, and meansto limit the transverse movement of the locking arm whereby oncontinuedrotatiori of the shaft the locking arm is moved longitudinallyby the eccentric to bear against the pad.

5. Apparatus as claimed in claim 4 1n WhlCh the arm comprises an outertubular member fixed on the collar and an inner cylindrical membertelescopically mounted in the outer member, the inner member having afollower rotatably mounted at one end thereof, and a circumferentiallyoriented cam recess in the eccentric portion of the shaft, thecylindrical member being biased to urge the follower into the cam recessto couple the collar yieldablywith the shaft.

6. Apparatus as claimed m claim 4 m wh ch the stop means comprises aflange fixed on the locking arm and located to meet the is movedtransversely thereov'er.

7. A 'aratus as claime pait m fint carries a pair of belaring pads andthe frame air of lockin mem ers. I I iigp ratus as clai med in claim 4in which the means to move t arm fixed on the sh being pivotablyFonnected to the fre d to the rame. i pressure die casting apparatus, adevice for moving and releasably locking a d le part to close a themounted on a die frame, comprising:

bearing pad when the lcoking arm d in claim 4, in which the the helocking member comprises a crank a second passage connecting the maincylinder chamber forwardly of the main piston with the auxiliarycylinder chamber rearwardly of the auxiliary piston;

the auxiliary piston rod being constructed and arranged to open andclose the first passage on movement of the auxiliary piston forwardlyand rearwardly respectively.

10. A device as claimed in claim 9 in which the first passage isenlarged between the auxiliary piston and the main cylinder chamber toform a flow chamber.

1. In pressure die casting apparatus, a device for moving and locking adie part to close a die mounted on a die frame, comprising: meansmounting the die part on the die frame; means to move the die part mountin a direction opposite to the force acting on the die part when closedand charged, to close the die; at least one locking member engagablewith the die part mount when the die is closed, said locking memberbeing pivotably mounted on the die frame, and means for moving thelocking member into a position between the mount and the frame wherebysaid force acts through the member onto the frame substantially in thedirection of said force.
 2. Apparatus as claimed in claim 1 in which thedie part mount carries at least one bearing means and the locking membercarries a locking arm movable to have one end thereof oPpose the bearingmeans, the locking arm being mounted eccentrically and substantially ona shaft and the shaft being rotatably mounted on the die frame. 3.Apparatus as claimed in claim 2 in which the shaft carries a transversecrank arm, a jack being pivotably mounted on the frame and on the crankarm for rotation of the shaft.
 4. Apparatus as claimed in claim 1 inwhich the die part mount carries a bearing pad and the frame carries alocking member comprising a shaft rotatably mounted on the die frame andhaving an eccentric portion, a collar rotatably mounted coaxially on theeccentric portion of the shaft, means yieldably coupling the collar withthe shaft, a locking arm radially fixed on the collar and movable onrotation of the shaft to have the free end of the locking arm oppose thebearing pad, and means to limit the transverse movement of the lockingarm whereby on continued rotation of the shaft the locking arm is movedlongitudinally by the eccentric to bear against the pad.
 5. Apparatus asclaimed in claim 4 in which the arm comprises an outer tubular memberfixed on the collar and an inner cylindrical member telescopicallymounted in the outer member, the inner member having a followerrotatably mounted at one end thereof, and a circumferentially orientedcam recess in the eccentric portion of the shaft, the cylindrical memberbeing biased to urge the follower into the cam recess to couple thecollar yieldably with the shaft.
 6. Apparatus as claimed in claim 4 inwhich the stop means comprises a flange fixed on the locking arm andlocated to meet the bearing pad when the lcoking arm is movedtransversely thereover.
 7. Apparatus as claimed in claim 4 in which thedie part mount carries a pair of bearing pads and the frame carries apair of locking members.
 8. Apparatus as claimed in claim 4 in which themeans to move the locking member comprises a crank arm fixed on theshaft and a hydraulic jack, the jack being pivotably connected to thefree end of the crank arm and to the frame.
 9. In pressure die castingapparatus, a device for moving and releasably locking a die part toclose a die mounted on a die frame, comprising: a main cylinder having aclosed chamber and an hydraulically actuated piston reciprocallyoperable in the chamber, the piston having a piston rod carrying a diepart mount; an auxiliary cylinder having a closed chamber and anhydraulically actuated piston reciprocally operable in the chamber, thepiston having a piston rod; first and second ports opening into theauxiliary cylinder chamber forwardly and rearwardly of the auxiliarypiston respectively; a third port opening through a first passage intothe main cylinder chamber rearwardly of the main piston; a secondpassage connecting the main cylinder chamber forwardly of the mainpiston with the auxiliary cylinder chamber rearwardly of the auxiliarypiston; the auxiliary piston rod being constructed and arranged to openand close the first passage on movement of the auxiliary pistonforwardly and rearwardly respectively.
 10. A device as claimed in claim9 in which the first passage is enlarged between the auxiliary pistonand the main cylinder chamber to form a flow chamber.